//leetcode 200 岛屿数量
public class Test3 {
    boolean[][] vis;
    int[] dx = {-1,1,0,0};
    int[] dy = {0,0,-1,1};
    int m,n;
    public int numIslands(char[][] grid) {
        m = grid.length;
        n = grid[0].length;
        vis = new boolean[m][n];
        int ret = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (!vis[i][j] && grid[i][j] == '1') {
                    ret++;
                    dfs(grid, i, j);
                }
            }
        }
        return ret;
    }

    public void dfs(char[][] grid, int i, int j) {
        vis[i][j] = true;
        for (int k = 0; k < 4; k++) {
            int x = i + dx[k];
            int y = j + dy[k];
            if (x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] && grid[x][y] == '1') {
                dfs(grid, x, y);
            }
        }
    }

}
